The Department of Microbiology and Immunology at the Medical College of Virginia Campus of Virginia Commonwealth University has maintained and operated a FACScan flow cytometer since 1988 and has used this equipment extensively (documentation attached). The instrument is now 13 years old and is in need of replacement. In addition, the replacement (FACScaliber) has an additional laser making possible four color analyses. The combination effect of heavy usage along with additional capacities, leads to this request for funds for purchase of the FACScaliber. The existing FACScan will be also kept as a backup plus overflow instrument. Usage is such that it is frequently difficult to obtain time on the instrument. The requested unit includes the 4 color cytometer, plus a Macintosh G4 computer/monitor plus Celiquest software plus peripherals for storage and print of files. User training and 2 year warranty is included. Our group consists of 10 funded investigators (NIH and one NSF) who are actively utilizing flow cytometry and have a number of publications using this technology. In addition, the unit is also available on a charge per hour basis to other users at MCV/NCU after appropriate training. At present, we have seven other laboratories that use the instrument on a less frequent basis.